The present invention relates to an information processing system having a sleep function and a resume function. The present invention also relates to an information processing method when in a sleep process and a resume process, and to a readable-by-computer recording medium.
A concept of saving the energy has spread over the recent years and, in an information processing system typified by a computer system of a personal computer and so on, it is an important matter to actualize a low consumption of the electric power as well as to enhance a portability thereof. Under such circumstances, there is a spread of the information processing system having a sleep function (that may also be termed a suspend function) capable of temporarily restraining a consumption of the electric power when unused.
This sleep function is to temporarily switch off power sources of some or all of the devices of the system. If the power sources of all the devices are switched off, the information needed for executing an operating system (OS) and application software running in the information processing system, is saved in other storage units from a main memory when requested to switch off the power sources, and then the main power source (system power source) is brought into an off-state.
Further, a resume function is necessary for restoring the information processing system from the sleep state. This resume function enables the state just before requesting the power-off to be instantaneously reproduced by restoring the necessary information. Accordingly, the user does not need operations of booting and stopping the OS and the application software, and there is no decline of operability of the user.
In the sleep state for actualizing a low consumption of the electric power, power supplies to a multiplicity of devices configuring the information processing system are stopped, and hence information (including data) on a volatile main memory is saved in a nonvolatile sub-storage unit (flash memory) and a nonvolatile storage medium. In the resume process for restoring from the sleep state, however, a process of reading the information from storage mediums such as a hard disk (HD), a floppy disk (FD) and others takes much time, and the start-up is time-consuming.
One method of reducing the time for the resume process is proposed in Japanese Patent Application Laying-Open Publication Nos. 6-131082 and 8-305469. Further, one method of reducing both of a write time and the consumption of the electric power by writing to the flash memory as a substitute for the storage medium when in the suspend process, is proposed in Patent Application Laying-Open Publication No. 11-85332.
On the other hand, a measure of retaining the information by keeping the power supply to the volatile main memory is taken for speeding up the start-up when in the resume process. There, however, remain the devices (such as a central processing unit (CPU) and so on) requiring the power supply even in the sleep state, and therefore the consumption of the electric power cannot be made approximate to zero. Besides, if unable to supply the power due to a service interruption and so on, it is inevitable that contents in the volatile main memory are to be lost.
In view of the prior art described above, it is necessary to not only prevent the information from being lost or damaged when cutting off the power supply but also actualize a further decrease in the consumption of the electric power by utilizing the nonvolatile sub-storage unit and storage medium.
Moreover, the write to the nonvolatile storage medium such as the hard disk absolutely takes much time, however, the start-up time in the resume process is required to decrease by use of the nonvolatile sub-storage unit such as the flash memory exhibiting a higher operating speed than the nonvolatile storage medium. The nonvolatile sub-storage unit is, however, expensive, and hence there might be a case where it is difficult to ensure a capacity large enough to supplement a storage capacity of the volatile main memory.